


Birthdayversary

by PanPacificPines



Category: Gravity Falls
Genre: F/M, pinecest - Freeform
Language: English
Status: Completed
Published: 2015-11-28
Updated: 2015-11-28
Packaged: 2018-05-03 18:35:26
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,254
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5302415
Author URL: https://archiveofourown.org/users/PanPacificPines/pseuds/PanPacificPines
Summary: <blockquote class="userstuff">
              <p>Dipper and Mabel have returned to Gravity Falls as adults. They've already been in a relationship for quite some time now, and their birthday is tomorrow. Dipper seems to have been planning something without Mabel's knowledge. He's got quite the surprise in mind.</p>
            </blockquote>





	Birthdayversary

**Author's Note:**

> So, I haven't written anything in a while, and I decided that coming back from my wedding was a good enough excuse to get out a oneshot or drabble. So here ya go! I hope you like it!

_Dear Mabel, it's been fifteen years since we came to Gravity Falls for the first time; half a lifetime ago. The first year was definitely the craziest. Dealing with interdimensional demon gods, gnomes, unicorns, even Lil' Gideon would have driven lesser twins totally insane. Good thing you were already pretty crazy already. Well, Lil' Gideon ain't so '"Lil' " anymore, and I think we've got a pretty good relationship with most of the spookums and magical creatures these days._

_Of course, I don't think my life really started until eight years later. Man, has it really been that long? You gave me the surprise of my life, Mabes. Hopefully I can give you yours too. Surprise, I mean. The best. Well, I've officially managed to figure out how to out awkward myself, cuz this is ink. Oh well. It's really just a few hours from now. I hope it goes well, or, I guess when you’re reading this I hope it went well._

 

Dipper clicked his pen and tucked it away in his shorts. He wrapped the leather cord around the matching brown journal and tucked it in between two of the spare towels in the bathroom closet. in his twenty-seven, almost twenty-eight years on earth he'd never really gotten the hang of hiding things from his twin, but somehow this one was going just as planned; even his little surprise. The black velvet covered ring box was stowed safely under a loose floorboard behind his bed in the attic of the shack. There were also a series of obstacles placed one on top of the other that'd each have to be moved and re-stacked precisely in the correct order, else he'd know there'd been tampering. Although that precaution was more of a decoy than anything else, as they were stacked on top of a nearby loose floorboard with a twenty dollar bill stuffed underneath it. The art of misdirection was a skill he'd honed well.

 

The twins have returned to Gravity Falls summer after summer for most of their lives. Their great uncles Stan and Ford lived there, and so did most of their best friends. Everyone assumed Dipper would follow in Ford's footsteps and get a doctorate at a ridiculously young age, and he still held that option in reserve. The six fingered genius had turned the lackluster and shockingly rusted out old Gravity Falls community college into a top ranked learning center with one of the best science programs in the country. The twins both nailed down their two year degrees in California right out of high school and toyed around with the idea of transferring full time to Grav-Tech for Bachelor's and up, though their studies started to flag just after their two year graduation.

 

Dipper's roommate had already left to go back home so it was the perfect opportunity for Mabel to sneak into her brother's dorm and take the biggest gamble of her life. All the hints had been there, but waiting for him naked as the day they were born with flower petals and almost entirely melted candles strewn all about his room was a big one. She'd smoked up a big bowl of college courage beforehand and put on her sexiest makeup for him; topped off with star shaped rhinestone stickers along her cheeks. When the courage seemed to cloud over her mind completely she even shaved a pine tree into her pubic hair and tinted it green with eyeshadow. Too far? Maybe, but it all paid off when her brother turned the key in his lock and entered a dim, candlelit apartment. To ensure the ambiance wasn't ruined Mabel had taped down the light switch. 

 

As soon as she heard "What the dukes?" (it was a phase Dipper was in. Don't question it.) she clicked the Bluetooth speakers on from her phone and the most romantic music she could think of started to play. It was only just barely ruined by the fact that "eat ya own pants" happened to be one of the lyrics in the song that actually started playing before a chorus of "rats! crap! damn, damn, damn!" rang out until some Jenny G saxaphone song started playing. 

 

The rest of that night would stay with them forever. Dipper couldn't exactly hide his reaction to Mabel's surprise and he knew it. Everything was perfect as far as Mabel was concerned. Her brover (like a lover who is also a bro. Don't worry, she didn't stick with that one for long) could barely get a word out other than the occasional "b-b-but, are you sure?" that was to be expected of such an undertaking. The next seven years were the best of their lives. Trying to hide their illicit love from friends and loved ones was difficult, but worth the perks. Mabel switched her major to film studies and Dipper took on a half dozen sciences so they could partner up and make a web based documentary series on "The Strange and Wonderful World of the Weird!!" as they put it. They managed to make a good living out of it too. Enough to keep themselves on the road for most of the year, doing online classes in whatever spare time that wasn't filled with love making.

 

This time he was gonna surprise her. It was their birthday tomorrow. By a happy coincidence (or planning on Mabel's part, he was never sure) it was also their anniversary. Or at least the anniversary of the first time they'd had sex. And the second, third and fourth times, college stamina being what it is. He'd already contacted Soos, Gideon, Wendy, Candy, Grenda and Pacifica. They were all going to be conveniently busy that day. Even the Grunkles had been notified that it was going to be a special twins only day and they'd been given the day off from their duties. Though no one was to tell Mabel so she didn't get the wrong idea and start making plans that might interfere. He brushed his teeth and washed his hands while going over the checklist in his head. It didn't even occur to him that he'd been in the bathroom for well over a half hour when he left and opened the door to the room he shared with his sister. memories came flooding back. That same barely covered up pungent smokey atmosphere, burnt down candles and soulful sax invaded all of his senses at once. His eyes took a moment to adjust. There was a trail of flower petals from the door to a big heart shape on his bed.

 

The door clicked behind him, followed a second later by another click that he knew to be the lock. Before he could turn around Mabel's scent invaded his world and her arms wrapped around his chest as her cheek pressed up against his back. Like silky snakes, her fingers traced up along his body and tangled in his hair in the way she knew turned his knees to jelly. 

"Hey, brother dearest. Know what time it is?" Her breasts were pressing into his back. That and the thing with the hair was already melting his brain, so no, he actually didn't have any idea. All that was left was-and there it was, the ear nibble followed by her breath on his neck.

"nngg- I-uh-Oh god, Mabes..."

"It's Eleven-Fifty." she coo'd. Agile fingers strolled down his body and his shorts were piled on top of his shirt in a matter of moments. The world spun round and the edge of the mattress caught the back of his knees and suddenly his head hit blankets. Petals that he suspected probably belonged to Lazy Susan's tulips hours earlier felt cool and rubbery against his back.

 

Then her tongue was his entire world. Slow trails up and down his member and around the rim of its head made him quiver and grip the sheets. 

"Oh~ oh god Mabel~" cool, slender fingers wrapped themselves around his manhood while nails grazed along the inside of his thigh.  Stars danced just behind his eyes and she circled around with her tongue once, twice, three times before sinking her lips down around his shaft. Part of him always had to fight back a giggle, since he knew she did that because of the owl in those lollipop commercials; but the rest of him moaned out her name, barely able to take in full breaths. His body twitched and writhed under her expert touch. Jolts of lightning seemed to radiate out from her into him.

 

A few luxurious dips of her mouth later she pulled back and the air was cold against the wetness between his legs. Her glorious brown locks draped around his face and they were nose to nose in an Eskimo kiss. 

"Hey Dippin' Dot?"

"Nnngggyeah?"

The springs of the bed creaked as she shifted her weight a bit and with barely any guidance from her deft fingers her warmth was all around him. Even as ready as she was for it, taking him in entirely in one go set her world on fire. She rocked her body, gripping his hips to steady herself. She took him in again and again, even her own breathing hitched here and there. She bit down on her lip and her eyes nailed shut. Her panting grew louder and louder, taking on a whining, pleading tone, for Dipper to last just a little bit longer as she practically slammed into him now. Slick wet sounds punctuated every whimper as her body tightened and tensed, each thrust of his, each rocking of her hips sent sparks and waves crashing together inside of her. Then all at once she practically screamed out wordlessly until she could bite it down, her nails digging into his sides as pure ecstasy shot through both of them.

 

Sweat felt cool against their skin in the cabin air when she rolled off of him and their fingers twined together, their body heat coming down just a little bit with each passing moment.

"Happy birthday." She smiled with her eyes, gazing lovingly into his.

"Happy birth-Gah! I-Oh my god, we didn't wear-"

"Hey! Shhh! Calm down. I took care of it, don't worry." Her smile faded a bit at the corners. "Besides, would it really be so bad if...?"

They'd talked about it before. How could they parent together as brother and sister? Would it be obvious? Would people find out? She'd always reasoned that she could be a 'single mother' with a deadbeat dad who ran away before the kid was born, but the thought had always scared Dipper too much for her to really push it much farther. though maybe that was unfair, it'd always scared her too. She had always pushed it to see if Dipper would be able to sooth her own worries on the matter.

"Actually...no, it really wouldn't be so bad. I'm sorry, I didn't mean to freak. I love you Mabes." If she ever doubted that he meant that, the shine of his eyes in that moment would have stomped those worries into dust with twelve inch heels.

"Hey, I-I love you too bro." She gave him a less than half hearted punch to the shoulder. "Why're you so chill all of a sudden? Not even a little panic attack?"

"Why, did you want me to have one?"

"Bluh, of course not. Just it's you, and sometimes that happens when I don't mean it to."

"Hey, I trust you. If you say you took care of it then you took care of it. Besides, we're two reasonably capable, intelligent young adults. We could handle it."

"....I'm not gonna say 'who are you and what have you done with Dipper?' because after what we just did that might be a little creepy." She climbed on top of him once more, though this time in a show of dominance, the heels of her hands pressing against his shoulders, her hair pushed back so they could meet eyes. "What are you hiding?"

 

He smirked. "Well, nothing right now, but if you back up just a little more..."

"Hey! I make with the jokes in this yuck hut. I know you, Dipper Pines, and you've got something up your proverbial sleeve."

"Would it be proverbial or metaphorical?"

She blinked twice then licked his entire face. They fought, rolling onto the floor and after one broke free from a pin to subdue the other, it was switched around again with a dirty trick, a tickle or a nipple tug, which was its own category of dirty trick. Mabel Finally won out again as Dipper lay sprawled on the wooden planks with cooling candle wax caking his various limbs. She sat down on his lap and wiggled a bit.

"I know you've been planning something."

"You know no such thing." He countered.

"Candy and Grenda are almost as big a gossip combined as Soos is, y'know. And Paz is still my darling sweetheart bestie who would tell me absolutely anything if I nibble the right ear. Or maybe it was the left..."

"Okay, first of all, that's still really hot."

"I know, Dips. I can feel that. And I also know about your Journal in the bathroom."

"W-What!?"

"And the box under the floorboards. By the way, I owe you twenty bucks."

"You-" He took a moment to glance over at his decoy setup, where it appeared undisturbed. "You monster."

 

"Brother-o-mine, I know you better than you could ever know yourself."

"Yeah, biblically..."

"Yeah" She took that moment to rub it in his face by pinching and twisting one of her own nipples this time, moaning with purpose. "And actually."

"Oh damn...Well, why are you even asking me if you already know everything?"

"Hey, I never said I actually peeked. More just that I wanted to confirm that you were trying to plan something behind my back, and that really is sweet you know."

"You're an evil genius."

She eased herself up and off of him, brushing the random detritus of the room off of her body before looking down to see her twin a bit more than half ready to go again. "Just as long as you know it, I'll let you keep your secret for now. But we both know who's the Alpha twin here. You may wanna get yourself cleaned up again." Her smile sent images of the cheshire cat streaming through his mind. The light from the window caught her just right so as to appear as a pair of eyes and set of pearly teeth backing up into the darkness of the room before fading away.

"And double damn."

 

Another half hour later found dipper cleaner than he was, and with a towel wrapped around his waist he saw, as expected, Mabel was sprawled across her bed, mouth agape and snoring. Though unlike him she had actually re-dressed in her fifth favorite stripey pink pajamas.

"That girl. Sometimes she's as predictable as the tides, and others..." A particularly raucous snore rattled the window. "She's like an earthquake....on fire."

 

 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

 

Luckily after their late night workout Dipper had no problems of his own falling asleep, and it was a restful slumber. Which was good, considering the hike they had to take to get up to the old abandoned railroad tracks and the saucer cut cliffs. He'd packed all of their picnic foods himself and he didn't even let her in the kitchen when he was making it ready. Not that it was anything particularly fancy or complicated. Croissants, grapes, cheese slices with cold cuts and the like wasn't exactly michelin star cuisine, but he felt like he needed at least a couple secrets left in his life that Mabel didn't instantly guess. The conversation seemed like a burning fuse for Dipper. He could hear himself talking, even responding to things she'd said, but nothing really registered. Mabel was half way through something about her camera equipment, or possibly a hair appointment with Pacifica when he brought out the ring box and opened it up.

 

"-Oh- My god, Dipper. What is this?"

The ring itself was silver, with two sweeping arms, wrapped around a single oval peridot. The arms were studded with smaller gems, but the lime green stone of the center seemed to glow.

"It's your birth stone." He cupped her hand lovingly and gently, as though she were cast in porcelain, and slipped the ring onto her finger.

"Yours too, Dipper. But...what IS this? God, it's beautiful."

"It's a star peridot. I had it done special. I didn't want one of those fancy cuts that'd just ruin the thing. When the light catches it you can see the star pattern refract out. I actually kinda wish it were more expensive...It feels like it should be more..."

"Dipper?"

"I love you, Mabel." He broke eye contact to rummage around in the bottom of the picnic bag to pull out the soft leather journal. There were the shapes of a pine tree and a star burnt into the front of it. "I put all of my feelings for you in here. I tried to make them all come out right. I just...You're perfect. I want to spend the rest of my life with you. And I know it's not a diamond or anything but-"

He was cut off by being bowled over by his sister and locked in a kiss that seemed to draw the life right out of him.

"Yes! I do! I want to spend the rest of our lives together! I love you Dipper!"

"You mean it?" His smile was weak and a bit scared, like always when he wasn't completely confident in the face of his own plans succeeding.

"I've wanted you to be my husband since we were four years old."

"Yeah, but you just wanted wedding cake."

"So what? We're made for eachother."

"Well, I can't exactly argue that." He stuck his tongue out at her.

"But...I mean. How will...?"

 

"Well, it couldn't be legal. I looked into it. I mean, maybe in Hawaii? I thought of asking the mayor to pass an ordnance for Gravity Falls, what with it being legal to marry woodpeckers...But that would bring up too many questions. But I did find some loopholes for us to have the same rights and all that."

"Woah, go mister research. Really, Hawaii? I mean, I wouldn't mind a trip out there AND getting hitched all in one go..."

"I could look into it again if you want? I just figured maybe a private ceremony for just the two of us."

"Don'tcha need like a minister or something? I feel like that's sorta traditional."

"Heh. Just pick one. If you think you figured things out quickly, the minute I started talking to Paz about today she got herself and practically all of our friends ordained. Turns out most of them already knew, I mean we KNOW why she knows... She insisted it be her that did it, and that there be a hot tub and a private hotel room for three afterwards."

Mabel was caught between a purr of approval and a riot of laughter at the whole thing. As it happened, her face couldn't decide either and the two expressions merged into something that put Dipper flat on his ass. As it happens Mabel decided to take advantage, pinning her dear brother to the grass.

"Our honeymoon is going to be legendary, bro-bro. Legendary."


End file.
